(a) Technical Field of the Invention
The present invention generally relates to washers, and more particularly to a method for producing circular washers having wedge planes, V-shaped grooves, and ridges on the top and bottom surfaces of the washers.
(b) Description of the Prior Art
FIG. 1 is a top view showing the steps of a conventional method in producing washers. As illustrated, in step A, at least two sets of two guiding holes 11 are formed at corresponding locations along the two edges of a belt of material 10. The guiding holes 11 are for guiding the subsequent process. A through hole 12 is then formed in step B by stamping between every two adjacent sets of guiding holes 11 in the middle of the belt 10. A residual slot 13 and a second residual slot 14 are also formed correspondingly by stamping at the two sides of every through hole 12 along the two edges of the belt 10 respectively. Then, in steps C and D, third residual slots 15 are formed between every two adjacent through holes 12 so that a circular ring 16 is formed around every through hole 12 which is still attached to the belt 10 by four legs 17. In step E, a number of sloped surfaces are formed radially around each ring 16 by cold forging. The sloped surfaces are further forged in step F so that desired precision and dimension are achieved. After a do-nothing step G, a through hole 18 of larger aperture is formed around each through hole 12 in step H. Then, after another do-nothing step I, the material around each ring 16 is stamped off in step J. Then, the belt 10 is cut down to separate the washer in step K.
The foregoing method indeed can produce washers having variable thickness. However, the method has a number of shortcomings. First, the foregoing process is too complicated. Additionally, as people of the related arts should know, the two do-nothing steps add unnecessary cost to the process. Secondly, as the sloped surfaces are forged before fine-tuning for the desired precision and dimension, the rings cannot be positioned accurately so that the rings might be damaged during the fine-tuning process, causing a less satisfactory yield. Thirdly, each ring is supported by four legs which are connected to where the ring has the smallest thickness. Residuals at these locations therefore cannot be dispersed easily and the accumulated residuals might deform the ring.
FIG. 2 are perspective views showing the top and bottom surfaces of an improved circular washer 6. The washer 6 has sloped surfaces 61, ridges 62, and V-shaped grooves 63 to achieve superior effectiveness and reliability than the conventional ones. However, the foregoing method is not appropriate for producing circular washers 6 having sloped surfaces, ridges, or grooves.